Method of manufacturing a semiconductor device utilizing outdiffusion to convert an epitaxial layer

Abstract

A method of manufacturing a semiconductor device having two juxtaposed regions (12, 16) of opposite conductivity types which adjoin a surface and which together constitute a p-n junction (9) which is preferably perpendicular to the surface and the doping concentration of which decreases towards the surface. According to the invention n-type and p-type buried layers (2, 6) are provided beside each other on a semiconductor substrate (1) and on said layers a high-ohmic epitaxial layer (7) is grown. By heating, the dopants diffuse from the buried layers through the whole thickness of the epitaxial layer and into the substrate. With suitably chosen donor and acceptor atoms (for example boron and phosphorus in silicon) n and p-type regions (12, 16) are formed in the epitaxial layer and form a p-n junction (9) perpendicular to the surface by compensation of the lateral diffusions from the buried layers.

What is claimed is: 
     
       1. A method of manufacturing a semiconductor structure, characterized as comprising the steps of: introducing (1) a first dopant of a first conductivity type into part of a monocrystalline substrate region of a semiconductor body to define a first zone of the first conductivity type and (2) a second dopant of a second conductivity type opposite to the first conductivity type into part of the substrate region to define a second zone of the second conductivity type;   growing an epitaxial semiconductor layer on the substrate region such that the first and second zones are first and second buried zones, respectively;   causing the dopants to diffuse sufficiently into the epitaxial layer to establish (1) the entire portion overlying the first buried zone as a first epitaxial region of the first conductivity type and (2) the entire portion overlying the second buried zone as a second epitaxial region of the second conductivity type, the buried zones being sufficiently near each other that the epitaxial regions adjoin each other along substantially the entire thickness of the epitaxial layer to form a p-n junction, the species and concentrations of the dopants being so chosen that their lateral diffusions in the epitaxial layer substantially compensate each other fully along the p-n junction so that it is substantially perpendicular to the upper surface of the epitaxial layer; and   forming at least one surface-adjacent zone of at least one electronic circuit element in at least one of the epitaxial regions, the resulting upper surface of the epitaxial layer being a monocrystalline semiconductor surface.   
     
     
       2. A method as in claim 1 characterized in that the step of forming comprises forming at least one surface-adjacent zone of at least one electronic circuit element in each epitaxial region. 
     
     
       3. A method as in claim 2 characterized in that the step of forming comprises introducing (1) a dopant of the second conductivity type into at least one portion of the first epitaxial region and (2) a dopant of the first conductivity type into at least one portion of the second epitaxial region. 
     
     
       4. A method as in claim 1 characterized in that the p-n junction terminates at the semiconductor surface. 
     
     
       5. A method of manufacturing a semiconductor structure, characterized by the steps of: introducing (1) a first dopant of a first conductivity type into a monocrystalline substrate region of a semiconductor body to define a substrate layer along an upper surface of the substrate region and (2) a second dopant of a second conductivity type opposite to the first conductivity type into the substrate region to define a substrate section below a part of the substrate layer;   substantially removing the part of the substrate layer above the substrate section;   growing an epitaxial layer over the remainder of the substrate layer and over the substrate section, the remainder of the substrate layer being a first buried zone of the first conductivity type, and the substrate section being a second buried zone of the second conductivity type; and   causing the dopants to diffuse sufficiently into the epitaxial layer to establish (1) the entire portion of the epitaxial layer overlying the first buried zone as a first epitaxial region of the first conductivity type and (2) the entire portion of the epitaxial layer overlying the second buried zone as a second epitaxial region of the second conductivity type, the buried zones being sufficiently near each other that the first and second epitaxial regions adjoin each other along substantially the entire thickness of the epitaxial layer to form a p-n junction terminating at the upper surface of the epitaxial layer.   
     
     
       6. A method as in claim 5 characterized in that the step of introducing is performed by introducing the first dopant into the substrate region, forming a mask along the upper surface such that the mask has a window generally above the intended location for the substrate section, and introducing the second dopant into the substrate region through the window. 
     
     
       7. A method as in claim 6 characterized in that the step of substantially removing is performed with the mask in place by removing the part of the substrate layer below the window. 
     
     
       8. A method as in claim 7 characterized by the step of forming an insulating layer along the upper surface prior to formation of the mask, the part of the insulating layer below the window being removed during the step of substantially removing. 
     
     
       9. A method as in claim 5 characterized by the step of forming (1) a pair of source/drain regions of the second conductivity type for a first insulated gate field-effect transistor in the first epitaxial region and (2) a pair of source/drain regions of the first conductivity type for a second insulated gate field-effect transistor in the second epitaxial region. 
     
     
       10. A method as in claim 1, 2, 5, 6 or 9 characterized in that the epitaxial layer comprises silicon, the first dopant comprises phosphorus, and the second dopant comprises boron. 
     
     
       11. A method as in claim 9, characterized by the steps of: forming an insulating layer along the epitaxial layer at its upper surface prior to causing the dopants to diffuse to establish the epitaxial regions; and selectively implanting boron ions into the epitaxial regions at locations for channel regions for the transistors to establish their threshold voltages. 
     
     
       12. A method as in claim 5, characterized in that the substrate region is of the first conductivity type, the first buried zone is formed so as to comprise a buried portion fully laterally enclosed by the second buried zone whereby the first epitaxial region comprises an epitaxial portion fully laterally enclosed by the second epitaxial region, the epitaxial portion serves as a channel region for a junction field-effect transistor, and a pair of source/drain electrodes for the transistor are formed on the epitaxial layer at its upper surface and on the substrate region at its lower surface. 
     
     
       13. A method as in claim 5 or 6 characterized in that the dopants have substantially the same diffusion coefficients in the epitaxial layer at any chosen diffusion temperature. 
     
     
       14. A method as in claim 13 characterized in that the buried zones have substantially the same net dopant concentrations at their upper surfaces. 
     
     
       15. A method as in claim 5, 6, 9, or 12 characterized in that the p-n junction is substantially perpendicular to the upper surface of the epitaxial layer. 
     
     
       16. A method as in claim 1 or 5 characterized in that the buried zones substantially adjoin each other. 
     
     
       17. A method of manufacturing a semiconductor structure, comprising the steps of: introducing (1) a first dopant of a first conductivity type into part of a monocrystalline substrate region of a semiconductor body to define a first zone of the first conductivity type and (2) a second dopant of a second conductivity type opposite to the first conductivity type into part of the substrate region to define a second zone of the second conductivity type juxtaposed in projection to the first zone;   growing an epitaxial semiconductor layer on the substrate region such that the first and second zones are first and second buried zones, respectively, the upper surface of the epitaxial layer forming the upper surface of the semiconductor body;   causing the dopants to diffuse sufficiently into the epitaxial layer to establish (1) the entire portion of the epitaxial layer overlying the first buried zone as a first epitaxial region of the first conductivity type and (2) the entire portion of the epitaxial layer overlying the second buried zone as a second epitaxial region of the second conductivity type, the buried zones being sufficiently near each other that the first and second epitaxial regions adjoin each other along substantially the entire thickness of the epitaxial layer to form a p-n junction terminating at the upper surface of the epitaxial layer, the species and concentrations of the dopants being so chosen that their lateral diffusions in the epitaxial layer substantially compensate each other fully along the p-n junction so that it is substantially perpendicular to the upper surface of the epitaxial layer; and   forming at least one surface-adjacent zone of at least one electronic circuit element in at least one of the epitaxial regions.   
     
     
       18. A method as in claim 17 wherein the step of forming comprises forming at least one surface-adjacent zone of at least one electronic circuit element in each epitaxial region. 
     
     
       19. A method as in claim 18 wherein the step of forming comprises introducing (1) a dopant of the second conductivity type into at least one portion of the first epitaxial region and (2) a dopant of the first conductivity type into at least one portion of the second epitaxial region. 
     
     
       20. A method as in claim 17 wherein the epitaxial layer comprises silicon, the first dopant comprises phosphorus, and the second dopant comprises boron. 
     
     
       21. A method as in claim 17 wherein the dopants have substantially the same diffusion coefficients in the epitaxial layer at any chosen diffusion temperature. 
     
     
       22. A method as in claim 21 wherein the buried zones have substantially the same net dopant concentrations at their upper surfaces.